Synchrotron radiation circular dichroism spectroscopy reveals that gold and silver nanoparticles modify the secondary structure of a lung surfactant protein B analogue

Inhaled nanoparticles (NPs) depositing in the alveolar region of the lung interact initially with a surfactant layer and in vitro studies have demonstrated that NPs can adversely affect the biophysical function of model pulmonary surfactants (PS), of which surfactant protein B (SP-B) is a key component. Other studies have demonstrated the potential for NPs to modify the structure and function of proteins. It was therefore hypothesised that NPs may affect the biophysical function of PS by modifying the structure of SP-B. Synchrotron radiation circular dichroism (SRCD) spectroscopy was used to explore the effect of various concentrations of gold nanoparticles (AuNPs) (5, 10, 20 nm), silver nanoparticles (AgNPs) (10 nm) and silver citrate on the secondary structure of surfactant protein B analogue, SP-B_1-25, in a TFE/PB dispersion. For Au and Ag NPs the SRCD spectra indicated a concentration dependent reduction in the α-helical structure of SP-B_1-25 (5 nm AuNP ≈ 10 nm AgNP ≫ 10 nm AuNP > 20 nm AuNP). For AuNPs the effect was greater for the 5 nm size, which was not fully explained by consideration of surface area. The impact of the 10 nm AgNPs was greater than that of the 10 nm AuNPs and the effect of AgNPs was greater than that of silver citrate at equivalent Ag mass concentrations. For 10 nm AuNPs, SRCD spectra for dispersions in, the more physiologically relevant, DPPC showed a similar concentration dependent pattern. The results demonstrate the potential for inhaled NPs to modify SP-B_1-25 structure and thus potentially adversely impact the physiological function of the lung, however, further studies are necessary to confirm this.

Combined micro-PET/micro-CT imaging of lung tumours in SPC-raf and SPC-myc transgenic mice

Introduction

SPC-raf and SPC-myc transgenic mice develop disseminated and circumscribed lung adenocarcinoma respectively, allowing for assessment of carcinogenesis and treatment strategies. The purpose of this study was to investigate the technical feasibility, the correlation of initial findings to histology and the administered radiation dose of combined micro-PET/micro-CT in these animal models.

Material and Methods

14 C57BL/6 mice (4 nontransgenic, 4 SPC-raf transgenic, 6 SPC-myc transgenic) were examined using micro-CT and ¹⁸F-Fluoro-deoxyglucose micro-PET in-vivo. Micro-PET data was corrected for random events and scatter prior to reconstruction with a 3D-FORE/2D-OSEM iterative algorithm. Rigid micro-PET/micro-CT registration was performed. Tumour-to-non-tumour ratios were calculated for different lung regions and focal lesions. Diffuse tumour growth was quantified using a semiautomated micro-CT segmentation routine reported earlier. Regional histologic tumour load was assessed using a 4-point rating scale. Gamma radiation dose was determined using thermoluminescence dosimeters.

Results

Micro-CT allowed visualisation of diffuse and circumscribed tumours in SPC-raf and SPC-myc transgenic animals along with morphology, while micro-PET provided information on metabolism, but lacked morphologic detail. Mean tumour-to-non-tumour ratio was 2.47 for circumscribed lesions. No significant correlation could be shown between histological tumour load and tumour-to-nontumour ratio for diffuse tumours in SPC-raf transgenic animals. Calculation of the expected dose based on gamma dosimetry yielded approximately 140 mGy/micro-PET examination additional to approximately 200 mGy due to micro-CT.

Conclusions

Combined micro-PET/micro-CT imaging allows for in-vivo assessment of lung tumours in SPC-raf and SPC-myc transgenic mice. The technique has potential for the evaluation of carcinogenesis and treatment strategies in circumscribed lung tumours.

Structural and Ontogenetic Relationships of Rat Lung Surfactant Apoproteins

Glycoproteins of molecular weights (MW) of 38,000, 32,000, and 26,000 are found in surfactant isolated from rat lungs. These proteins were further examined for their specificity to pulmonary surfactant, structural and metabolic interrelationships, and relation to the ontogenesis of pulmonary surfactant. With ultracentrifugations in salt and sucrose density gradients, a preparation of pulmonary surfactant was isolated from rat lung lavage fluid, which was rich in surfactant lipids (phosphatidylcholine and phosphatidylglycerol), and contained exclusively the 38,000-, 32,000-, 26,000-, and 10,000- to 12,000-dalton proteins. The 38,000-, 32,000-, and 26,000-dalton proteins are not serum proteins. Using an antiserum specific for the combined 38,000-, 32,000-, and 26,000-dalton proteins and the immunoperoxidase technique, the source of one or more of these three proteins was found to be alveolar epithelial type II cells, the cells involved in the synthesis and secretion of pulmonary surfactant. These proteins, when dissociated from lipids, show considerable self-association and form homopolymers. On isoelectric focusing, these proteins show considerable charge heterogeneity, which, in large part, is due to terminally linked sialic acid residues. Partial proteolysis of these proteins and subsequent analyses of the released polypeptides suggest the existence of large segments of homology between the 38,000-, and 32,000-dalton proteins. The relationship of the 38,000-, and 32,000-dalton proteins with the 26,000-, and 10,000- to 12,000-dalton proteins is not clear as yet. The results of protein analyses of purified tubular myelin and of lamellar bodies suggest that the 26,000-dalton protein may be derived extracellularly, possibly from other surfactant proteins by the action of enzymes present in the alveolar lining layer. We observed no reactivity of the antibody raised against the 38,000-, 32,000-, and 26,000-dalton proteins with the 10,000- to 12,000-dalton protein. The 38,000-, 32,000-, and 26,000-dalton proteins appear during fetal lung maturation at the same gestational time as the surfactant is known to appear, and their combined content increases thereafter in fetal lungs and in amniotic fluid. It appears that the less glycosylated (32,000-dalton protein) of the 38,000- and 32,000-dalton proteins appears first during fetal lung development.

[Advancement in study of inhalation injury]

Inhalation injury is a major contributor to the morbidity and mortality associated with serious burns. The improvement in the understanding of smoke inhalation injury had been obtained in the last half century in China. The models of steam and smoke inhalation injury had been reproduced and a series of experimental studies had been performed. It was found that chemical bronchiotracheitis, pulmonary edema and alveolar collapse (atelectasis) were the primary pathologic findings after inhalation injury. The second inflammatory response would play an important role in the development of acute respiratory failure. The roles of some cytokines, inflammatory cells and pulmonary surfactants in the development of inhalation injury had been elucidated. The etiologic factors and the pathophysiologic changes in inhalation injury had been illustrated clearly. These basic science investigations had led to the advances in protective strategies for the complications of inhalation injury. Now the morbidity and mortality of inhalation injury have decreased markedly in China.

Thermodynamic studies of bovine lung surfactant extract mixing with cholesterol and its palmitate derivative

Langmuir film behavior of bovine lipid extract surfactant (BLES), mixed with cholesterol (CHOL) and cholesterol palmitate (CHOLP), has been studied by surface pressure (pi)-area (A) measurements. Associative interactions, observed for both systems, were less favored at lower BLES content. The presence of unsaturated phospholipids and surfactant proteins in BLES favored the association. Miscibility of BLES was better with CHOLP than with CHOL at all compositions, indicating more compact packing of the BLES-CHOLP than of the BLES-CHOL system. The most stable mixtures were found at 30-40 mol% CHOL and at low pi and at 20-25 mol% CHOLP but at higher pi. These results suggest that BLES-CHOL miscibility is better at low pi and low CHOL concentrations, while BLES-CHOLP miscibility is better at high pi and high CHOLP concentrations.

Monitoring alveolar epithelial function in acute lung injury

OBJECTIVE

Identification of humoral markers of acute lung injury may lead to insights into pathologic mechanisms. In addition, specific markers may be useful for predicting development of acute respiratory distress syndrome (ARDS) or for assessing prognosis. Ultimately, studies of lung injury markers may help define interventions that prevent or moderate ARDS. The alveolar epithelium is important both for the integrity of the blood-gas barrier and for repair of the barrier after lung injury. This article reviews markers that derive from or relate to the alveolar epithelium and that might be used for monitoring alveolar epithelial function in acute lung injury. Surfactant apoproteins may be important markers of injury or for prognosis. Levels of surfactant apoprotein A (SP-A) fall 50-75% in patients with severe lung injury compared to normal patients. Serum levels of SP-A in patients dying of acute respiratory distress syndrome are double serum levels of survivors.

Establishment of an immortalized cell line and transplantable xenograft from a bronchioloalveolar lung carcinoma of a cat

OBJECTIVE

To establish an immortalized cell line and transplantable xenograft of feline bronchioloalveolar lung carcinoma (BAC).

SAMPLE POPULATION

Pleural effusion from a 12-year-old Persian male cat with BAC.

PROCEDURE

Tumor cells from the pleural effusion were grown in monolayer cell culture and injected into severe combined immunodeficient (SCID) mice to establish an immortalized cell line as well as a transplantable xenograft.

RESULTS

Both the primary lung carcinoma, the derived cell line, and the transplantable xenograft had evidence of a type-II pneumocyte origin expressing lamellar bodies ultrastructurally and thyroid transcription factor-1 and surfactant immunocytochemically. All 3 also expressed nuclear p53 immunoreactivity. A metaphase spread of the cell line (SPARKY) probed with fluorescein-labeled genomic feline DNA gave evidence of its feline origin. Flow cytometric studies indicated aneuploidy with a DNA index of 1.6. An R-banded karyotype revealed a modal number of 66 including the feline Y chromosome. The cell line had a doubling time of 16 hours. The xenograft (SPARKY-X) reached a diameter of 1 cm in 3 weeks in SCID mice. Deoxyribonucleic acid fingerprint analysis revealed that SPARKY and SPARKY-X were novel and strongly matched each other, except for the murine component found in SPARKY-X. Interestingly, SPARKY-X manifested the characteristic lepidic growth pattern of pulmonic BAC.

CONCLUSIONS

Both the cell line and xenograft retained their autochthonous BAC phenotype, making them useful for the subsequent dissection of molecular abnormalities in feline BAC and in vitro screening of chemotherapeutic agents.

Assessment of transcriptional gene activity in situ by application of HOPE-fixed, paraffin-embedded tissues

We report the use of HOPE-fixation (HOPE = Hepes-Glutamic acid buffer mediated Organic solvent Protection Effect) for specimens utilized for in situ hybridization targeting mRNA. For this purpose, an optimized protocol was developed and repeatedly tested on HOPE-fixed lung specimens. We observed that neither pretreatment, permeabilizing the cells, nor prehybridization is necessary to generate signals. After deparaffinizing, the random primed digoxigenin-labeled probes are directly hybridized together with yeast tRNA for blocking unspecific signals. Detection was performed using anti digoxigenin antibodies conjugated with alkaline phosphatase and new-fuchsine or NBT/BCIP as substrates. The results were verified by RT-PCR and adequate negative controls. Signals for human surfactant protein-A and interferon-gamma-inducible protein-10 developed rapidly within 10 min, accompanied by high signal intensities comparable to those observed in immunohistochemistry. Signal enhancement by biotinyl-tyramide, although giving suitable results as well, did not lead to higher signal intensities, and thus was not necessary in conjunction with the probes tested so far. These experiments were performed with material stored under appropriate conditions (at +4 degrees C) up to five years. To sum up, these initial results, obtained with the novel HOPE-fixative, are promising as regards the enhancement of the capabilities of in situ hybridization in the future.

Surfactant protein a inhibits lipopolysaccharide-induced immune cell activation by preventing the interaction of lipopolysaccharide with lipopolysaccharide-binding protein

Pulmonary surfactant protein (SP)-A, an innate immune molecule, modifies lipopolysaccharide (LPS)-induced cell responses. Because SP-A avidly binds to the deep rough (Re) mutant of LPS, we first investigated the functional consequences of this interaction and found that preincubation of Re-LPS with SP-A significantly and in a dose-dependent manner decreased the sensitivity of rat alveolar macrophages and human mononuclear cells to Re-LPS-induced activation at limited amounts of LPS-binding protein (LBP). At high LBP concentrations, the SP-A-mediated cellular inhibition of Re-LPS-induced activation was abrogated. Because LBP-catalyzed binding of LPS to CD14 is essential for low-dose LPS-induced signaling, we then hypothesized that SP-A inhibits Re-LPS-induced immune cell activation via inhibiting the binding of Re-LPS to LBP. Binding competition experiments employing a surface plasmon resonance technique showed that Re-LPS preincubated with SP-A bound to LBP to a significantly lesser extent than Re-LPS alone. For enhanced cellular association of [(3)H]LPS/SP-A complexes to occur, the expression of membrane-bound CD14 by human embryonic kidney cells 293 was not essential. Therefore, the ability of SP-A to inhibit immune cell activation by Re-LPS may be due to its ability to block the binding of Re-LPS to LBP and prevent the initiation of the LBP/CD14 pathway for inflammatory reactions in the lung.

Surfactant protein A decreases lung injury and mortality after murine marrow transplantation

Surfactant protein A (SP-A), a collectin associated with surfactant lipids, can have immune modulatory effects. We hypothesized that exogenous and basal endogenous SP-A can function to suppress donor T-cell-dependent inflammation that occurs during the generation of idiopathic pneumonia syndrome after bone marrow transplantation (BMT). Wild-type and SP-A-deficient mice were conditioned with cyclophosphamide and lethal irradiation and then given allogeneic donor bone marrow plus inflammation-inducing spleen T cells. On Day 7 after BMT, bronchoalveolar lavage fluids from SP-A-deficient mice contained increased numbers of inflammatory cells and higher levels of proinflammatory mediators tumor necrosis factor-alpha, interferon-gamma, and nitric oxide than wild-type mice. Exaggerated inflammation in SP-A-deficient mice was associated with decreased dynamic lung compliance and increased donor T-cell-dependent mortality (P = 0.0007, n = 10). Nitrative stress in alveolar macrophages from SP-A(-/-)-conditioned BMT recipients was higher than for SP-A(+/+) mice. Similarly, mice treated with transtracheal human SP-A (50 micro g), instilled on Day 4 after BMT during a time of in vivo donor T cell activation, exhibited decreased inflammation and improved early survival compared with buffer-instilled mice. We concluded that basal endogenous SP-A and enhanced alveolar SP-A level modulate donor T-cell-dependent immune responses and prolong survival after allogeneic BMT.

The intrauterine expression of surfactant protein D in the terminal airways of human fetuses compared with surfactant protein A

We investigated the expression of surfactant protein (SP)-D in pulmonary epithelial cells, compared with the expression of SP-A. A total of 15 fetuses aborted at 8, 15, 19, 20, 21 and 23 weeks gestation and four premature babies who were stillborn or died after birth between May 1997 and October 2001 were included in this study. Fetuses showing any findings associated with preterm premature rupture of membranes or infection were excluded. We performed immunohistochemical examinations for SP-D and SP-A. SP-D was not detected by immunostaining at 8, 15 and 19 weeks gestation. At 21 weeks gestation, SP-D was weakly localized, in some cases (5/9), in the epithelial lining of both bronchioles and terminal airways. In contrast at 21 weeks gestation, SP-A was more markedly detected in the epithelial lining of both bronchioles and terminal airways in all cases but not detected in bronchioles and terminal airways at 8, 15 and 19 weeks gestation.

CONCLUSION

the findings in this investigation suggests that the production of SP-D in fetal human lungs begins in the bronchiolar and terminal epithelium from about 21 weeks of gestation.

TNF-alpha inhibits SP-A gene expression in lung epithelial cells via p38 MAPK

Surfactant protein A (SP-A), the major lung surfactant-associated protein, mediates local defense against pathogens and modulates inflammation in the alveolus. Tumor necrosis factor (TNF)-alpha, a proinflammatory cytokine, inhibits SP-A gene expression in lung epithelial cells. Inhibitors of the phosphatidylinositol 3-kinase pathway, i.e., wortmannin, LY-294002, and rapamycin, did not block the inhibitory effects of TNF-alpha on SP-A mRNA levels. An inhibitor of the p44/42 mitogen-activated protein kinase (MAPK) pathway, PD-98059, was also ineffective. PD-169316 and SB-203580, inhibitors of p38 MAPK, blocked the TNF-alpha-mediated inhibition of SP-A mRNA levels. TNF-alpha increased the phosphorylation of p38 MAPK within 15 min. Anisomycin, an activator of p38 MAPK, increased p38 MAPK phosphorylation and decreased SP-A mRNA levels in a dose-dependent manner. Finally, TNF-alpha increased the phosphorylation of ATF-2, a transcription factor that is a p38 MAPK substrate. We conclude that TNF-alpha downregulates SP-A gene expression in lung epithelial cells via the p38 MAPK signal transduction pathway.

The role of pulmonary collectin N-terminal domains in surfactant structure, function, and homeostasis in vivo

The N-terminal domains of the lung collectins, surfactant proteins A (SP-A) and D (SP-D), are critical for surfactant phospholipid interactions and surfactant homeostasis, respectively. To further assess the importance of lung collectin N-terminal domains in surfactant structure and function, a chimeric SP-D/SP-A (D/A) gene was constructed by substituting nucleotides encoding amino acids Asn(1)-Ala(7) of rat SP-A with the corresponding N-terminal sequences from rat SP-D, Ala(1)-Asn(25). Recombinant D/A migrated as a 35-kDa band on reducing SDS-PAGE and as a ladder of disulfide-linked multimers under nonreducing conditions. The recombinant D/A bound and aggregated phosphatidylcholine containing vesicles as effectively as rat SP-A. Mice in which endogenous pulmonary collectins were replaced with D/A were developed by human SP-C promoter-driven overexpression of the D/A gene in SP-A(-/-) and SP-D(-/-) animals. Analysis of lavage fluid from SP-A(-/-,D/A) mice revealed that glycosylated, oligomeric D/A was secreted into the air spaces at levels that were comparable with the authentic collectins and that the N-terminal interchange converted SP-A from a "bouquet" to a cruciform configuration. Transmission electron microscopy of surfactant from the SP-A(-/-,D/A) mice revealed atypical tubular myelin containing central "target-like" electron density. Surfactant isolated from SP-A(-/-,D/A) mice exhibited elevated surface tension both in the presence and absence of plasma inhibitors, but whole lung compliance of the SP-A(-/-,D/A) animals was not different from the SP-A(-/-) littermates. Lung-specific overexpression of D/A in the SPD(-/-) mouse resulted in hetero-oligomer formation with mouse SP-A and did not correct the air space dilation or phospholipidosis that occurs in the absence of SP-D. These studies indicate that the N terminus of SP-D 1) can functionally replace the N terminus of SP-A for lipid aggregation and tubular myelin formation, but not for surface tension lowering properties of SP-A, and 2) is not sufficient to reverse the structural and metabolic pulmonary defects in the SP-D(-/-) mouse.

Surfactant synthesis and kinetics in infants with congenital diaphragmatic hernia

In animal models of congenital diaphragmatic hernia (CDH), surfactant deficiency contributes to the pathophysiology of the disease; however, information on CDH in humans is limited. We compared surfactant disaturated phosphatidylcholine (DSPC) synthesis and metabolism, by stable isotope technology, in newborn infants with CDH and in control subjects. DSPC amount, total proteins, and surfactant protein-A (SP-A) from tracheal aspirates were also measured. DSPC and SP-A were significantly lower in 14 infants with CDH than in the eight control subjects. Mean DSPC was 2.3 +/- 1.3 mg/ml of epithelial lining fluid (ELF) in infants with CDH and 4.6 +/- 1.5 mg/ml of ELF in control subjects (p = 0.001). Mean SP-A in infants with CDH and in control subjects was 16.2 +/- 9.3 and 61.2 +/- 30.6 microg/ml of ELF, respectively (p = 0.03). DSPC kinetics was measured in 12 of 14 infants with CDH and in 5 of 8 control subjects. Secretion time was 8.3 +/- 5.5 and 8.5 +/- 2.5 hours and peak time 51.9 +/- 15.2 and 51 +/- 13 hours in infants with CDH and in control subjects, respectively. Fractional synthesis rate was not different for infants with CDH and control subjects (p = 0.4). In conclusion, surfactant DSPC synthesis and kinetics were not significantly deranged in infants with CDH compared with control subjects. Other factors, such as lower surface area or increased DSPC catabolism, may contribute to surfactant pool alteration in CDH.

Tissue distribution of surfactant proteins A and D in the mouse

Surfactant proteins A and D, collagen-like lectins (collectins), were first isolated from the lung. In the lung, SP-A and SP-D have roles in surfactant homeostasis and innate immunity. In this study we show that SP-A and SP-D mRNA can be detected in a significant number of non-pulmonary tissues but the proteins have a more limited distribution. SP-D protein was detected in lung, uterus, ovary, and lacrimal gland, whereas SP-A protein was detected only in the lung. The results suggest that SP-D participates in mucosal immunity throughout the body.

Inflammatory reaction and alterations of pulmonary surfactant in Pseudomonas Aeruginosa pneumonia in immunocompromised rats

Pulmonary surfactant ( PS ) compromises lipids and surfactant proteins (SP) and lines on the alveolar air-liquid interface. It can reduce surface tension, prevent alveoli from collapse and reduce alveoli edema by disaturated dipalmitoylphosphatidylcholine. It also modulates the pulmonary immunology by SP-A and SP-D. In this study,we established a rat model of immunocompromised host (ICH) with pulmonary infection of Pseudomonas aeruginosa (P. aeruginosa), then studied its pulmonary inflammatory reaction and analyzed the concentration of lipids and SP-A in bronchoalveolar lavage fluid (BALF) during infection.

Lipid-restricted recognition of mycobacterial lipoglycans by human pulmonary surfactant protein A: a surface-plasmon-resonance study

The human pulmonary surfactant protein A (hSP-A), a member of the mammalian collectin family, is thought to play a key defensive role against airborne invading pulmonary pathogens, among which is Mycobacterium tuberculosis, the aetiologic agent of tuberculosis. hSP-A has been shown to promote the uptake and the phagocytosis of pathogenic bacilli through the recognition and the binding of carbohydrate motifs on the invading pathogen surface. Recently we identified lipomannan and mannosylated lipoarabinomannan (ManLAM), two major mycobacterial cell-wall lipoglycans, as potential ligands for binding of hSP-A. We demonstrated that both the terminal mannose residues and the fatty acids are critical for binding, whereas the inner arabinosyl and mannosyl domains do not participate. In the present study we developed a surface-plasmon-resonance assay to analyse the molecular basis for the recognition of ManLAM by hSP-A and to try to define further the role of the lipidic aglycone moiety. Binding of ManLAM to immobilized hSP-A was consistent with the simplest one-to-one interaction model involving a single class of carbohydrate-binding site. This observation strongly suggests that the lipid moiety of ManLAM does not directly interact with hSP-A, but is rather responsible for the macromolecular organization of the lipoglycan, which may be necessary for efficient recognition of the terminal mannosyl epitopes. The indirect, structural role of the lipoglycan lipidic component is further supported by the complete lack of interaction with hSP-A in the presence of a low concentration of mild detergent.

Pulmonary type II cell hypertrophy and pulmonary lipoproteinosis are features of chronic IL-13 exposure

Interleukin (IL)-13, a key mediator of Th2-mediated immunity, contributes to the pathogenesis of asthma and other pulmonary diseases via its ability to generate fibrosis, mucus metaplasia, eosinophilic inflammation, and airway hyperresponsiveness. In these studies, we compared surfactant accumulation in wild-type mice and mice in which IL-13 was overexpressed in the lung. When compared with littermate controls, transgenic animals showed alveolar type II cell hypertrophy under light and electron microscopy. Over time, their alveoli also filled with surfactant in a pulmonary alveolar proteinosis pattern. At the same time, prominent interstitial fibrosis occurs. Bronchoalveolar lavage fluid from these mice had a three- to sixfold increase in surfactant phospholipids. Surfactant proteins (SP)-A, -B, and -C showed two- to threefold increases, whereas SP-D increased 70-fold. These results indicate that IL-13 is a potent stimulator of surfactant phospholipid and surfactant accumulation in the lung. IL-13 may therefore play a central role in the broad range of chronic pulmonary conditions in which fibrosis, type II cell hypertrophy, and surfactant accumulation occur.

Combined SP-A-bleomycin effect on cytokines by THP-1 cells: impact of surfactant lipids on this effect

Surfactant protein A (SP-A) plays a role in host defense and inflammation in the lung. In the present study, we investigated the hypothesis that SP-A is involved in bleomycin-induced pulmonary fibrosis. We studied the effects of human SP-A on bleomycin-induced cytokine production and mRNA expression in THP-1 macrophage-like cells and obtained the following results. 1) Bleomycin-treated THP-1 cells increased tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, and IL-1beta production in dose- and time-dependent patterns, as we have observed with SP-A. TNF-alpha levels were unaffected by treatment with cytosine arabinoside. 2) The combined bleomycin-SP-A effect on cytokine production is additive by RNase protection assay and synergistic by enzyme-linked immunosorbent assay. 3) Although the bleomycin effect on cytokine production was not significantly affected by the presence of surfactant lipid, the additive and synergistic effect of SP-A-bleomycin on cytokine production was significantly reduced. We speculate that the elevated cytokine levels resulting from the bleomycin-SP-A synergism are responsible for bleomycin-induced pulmonary fibrosis and that surfactant lipids can help ameliorate pulmonary complications observed during bleomycin chemotherapy.

Raised plasma concentrations of alpha-defensins in patients with idiopathic pulmonary fibrosis

BACKGROUND

Neutrophils are thought to play an important role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Human neutrophils contain antimicrobial and cytotoxic peptides in the azurophil granules which belong to a family of mammalian neutrophil peptides named alpha-defensins. A study was undertaken to investigate the role of alpha-defensins in the pathogenesis of IPF.

METHODS

The concentrations of alpha-defensins (human neutrophil peptides (HNPs) 1, 2, and 3) in plasma and bronchoalveolar lavage (BAL) fluid of 30 patients with IPF and 15 healthy subjects were measured by radioimmunoassay.

RESULTS

The concentrations of alpha-defensins in plasma, but not in BAL fluid, were significantly higher in IPF patients than in controls. BAL fluid concentrations of interleukin (IL)-8 in patients with IPF, which were significantly higher than in controls, correlated with those of alpha-defensins. An inverse relationship was seen between plasma alpha-defensin levels and the arterial oxygen tension (PaO(2)) and pulmonary function (vital capacity (%VC), forced expiratory volume in 1 second (FEV(1)), and carbon monoxide transfer factor (%TLCO)) in patients with IPF. Plasma levels of alpha-defensins also correlated with the clinical course in IPF patients with an acute exacerbation. Immunohistochemically, positive staining was observed inside and outside neutrophils in the alveolar septa, especially in dense fibrotic areas.

CONCLUSION

These findings suggest that alpha-defensins play an important role in the pathogenesis of IPF, and that the plasma alpha-defensin level may be a useful marker of disease severity and activity.

Surfactant protein A regulates surfactant phospholipid clearance after LPS-induced injury in vivo

Previous in vitro studies have suggested that surfactant protein A (SP-A) may play a role in pulmonary surfactant homeostasis by mediating surfactant secretion and clearance. However, mice made deficient in SP-A [SP-A (-/-) animals] have relatively normal levels of surfactant compared with wild-type SP-A (+/+) animals. We hypothesize that SP-A may play a role in surfactant homeostasis after acute lung injury. Bacterial lipopolysaccharide was instilled into the lungs of SP-A (-/-) mice and SP-A (+/+) mice to induce injury. Surfactant phospholipid levels were increased 1.6-fold in injured SP-A (-/-) animals, although injury did not alter [3H]choline or [14C]palmitate incorporation into dipalmitoylphosphatidylcholine (DPPC), suggesting no change in surfactant synthesis/secretion 12 h after injury. Clearance of [3H]DPPC from the lungs of injured SP-A (-/-) animals was decreased by approximately 40%. Instillation of 50 microg of exogenous SP-A rescued both the clearance defect and the increased phospholipid defect in injured SP-A (-/-) animals, suggesting that SP-A may play a role in regulating clearance of surfactant phospholipids after acute lung injury.

Cutting edge: the immunostimulatory activity of the lung surfactant protein-A involves Toll-like receptor 4

The collectin surfactant protein-A (SP-A) is involved in the innate host defense and the regulation of inflammatory processes in the lung. In this work we investigated the molecular mechanisms related to the immunostimulatory activity of SP-A using macrophages from C3H/HeJ mice, which carry an inactivating mutation in the Toll-like receptor (TLR)4 gene, and TLR4-transfected Chinese hamster ovary cells. We demonstrate that SP-A-induced activation of the NF-kappaB signaling pathway and up-regulation of cytokine synthesis such as TNF-alpha and IL-10 are critically dependent on the TLR4 functional complex. These findings support the concept that TLR4 is a pattern recognition receptor that signals in response to both foreign pathogens and endogenous host mediators.

Surfactant proteins A and D in children with pulmonary disease due to gastroesophageal reflux

Children with gastroesophageal reflux often suffer from chronic, severe lung damage and recurrent infections. The mechanisms may involve reflux induced lung injury with alterations of the surfactant proteins (SP) SP-A and SP-D, which bind specifically to various microbes and increase their elimination by granular leukocytes and macrophages. In 20 children with gastroesophageal reflux disease (GERD) the bronchoalveolar lavage content and macromolecular organization of SP-A and SP-D was determined by enzyme linked immunosorbent assay and gel chromatography. For comparison, lavages from 17 children without respiratory diseases were investigated. Both, SP-A and SP-D were significantly reduced in children with GERD-median (25, 75 percentiles) SP-A: 362 (169, 494) ng/ml versus 867 (656, 1,761) in control subjects and SP-D: 174 (73, 456) ng/ml versus 518 (295, 748) ng/ml in control subjects. The more active, higher molecular weight oligomers of SP-A and especially those of SP-D were diminished, whereas the smaller sized forms of SP-D were markedly increased. In children with GERD, significantly reduced amounts of SP-A and SP-D and an altered structural organization of the surfactant protein oligomers were demonstrated. Such impairments of central components of the innate host defense system may contribute to the pathogenesis of the chronic lung disease commonly observed in these children.

Injury responses to different surfactants in ventilated premature lamb lungs

The lung of the preterm infant is easily injured and an initial indication of the injury is an inflammatory response. Surfactant treatment and gentle ventilation will minimize the initiation and progression of injury. We asked if the initial lung injury response differed when preterm ventilated lambs were treated with complete natural sheep surfactant, a lipid extract of sheep surfactant, a surfactant used to treat RDS (Survanta), or a synthetic surfactant containing recombinant SP-C (Venticute). We used a gentle style of ventilation and a positive end expiratory pressure of 4 cmH(2)0 to minimize injury. The surfactants were not distinguishable based on gas exchange, compliance or lung gas volumes over the 6h ventilation period. When compared with unventilated controls the ventilated lambs had increased protein and inflammatory cells in alveolar lavages. The cells from the alveolar lavages produced more H(2)0(2), expressed more surface adhesion antigens and CD-14 receptors, and expressed more mRNA for the pro-inflammatory cytokines IL-1 beta and IL-8 than did cells from unventilated lungs. Lung tissue expressed primarily increased IL-6 mRNA relative to unventilated controls. However, there were no consistent differences in any of the inflammatory indicators between the different surfactant treated groups. Because endotoxin free natural surfactant containing SP-A was not superior to three other surfactants containing differing amounts of the surfactant proteins, additions of these proteins to clinical surfactants may not decrease the indicators of lung inflammation that accompany the initiation of ventilation of the preterm lung.

A role for C/EBP delta in human surfactant protein A (SP-A) gene expression

C/EBP delta, a member of the leucine zipper transcription factor family, is expressed at higher levels in the lung than in any other tissue. We detected C/EBP delta mRNA and protein in NCI-H441 cells, a cell line derived from a human adenocarcinoma that produces surfactant protein A (SP-A). NCI-H441 cells were exposed to phosphorothioate-substituted antisense oligonucleotides directed against C/EBP delta. After exposure to the oligonucleotides, cells were harvested, total RNA prepared, and levels of mRNA for C/EBP delta, SP-A and a control, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), were quantified from Northern blots. An oligonucleotide that overlapped the translational start was effective in reducing C/EBP delta mRNA. Oligonucleotides that corresponded to regions upstream and downstream from the translational start were not as effective. The loss of C/EBP delta was accompanied by a decrease in the level of SP-A mRNA. The overlapping oligonucleotide was tested more extensively. After 72 h, antisense oligonucleotide at 3 and 5 microM reduced the level of C/EBP delta mRNA and protein by 50% or more as compared with sense and scrambled controls. The SP-A mRNA level was reduced even more, by about 75%. GAPDH mRNA was not affected. We conclude that C/EBP delta plays a role in the regulation of SP-A gene expression.

Members of the C/EBP transcription factor family stimulate expression of the human and rat surfactant protein A (SP-A) genes

Members of the CCAAT enhancer binding protein (C/EBP) transcription factor family were detected in fetal lung of both human and rat. In rat lung, the level of C/EBPs increased with time of gestation, peaking around birth. In adult rat lung, C/EBPs were localized to the alveolar type II cells. The effect of C/EBPs on pulmonary surfactant protein A (SP-A), which is also expressed late in gestation, was investigated. In contrast to control plasmids, C/EBP delta expressing plasmids reversed the action of a transcriptional silencer just upstream of the rat SP-A promoter. In order to test the effect of C/EBPs on endogenous SP-A gene expression, cells that express SP-A were exposed to a phosphorothioate-substituted, double-stranded oligonucleotide matching the consensus C/EBP binding site (decoy oligonucleotide) at concentrations from 0.5 to 10 microM for 72 h. A mutant oligonucleotide with an 8-base pair (bp) substitution served as a control. The decoy oligonucleotide reduced SP-A mRNA as much as 75% compared to a mutant oligonucleotide both in the human lung cell line, NCI-H441, and in primary human fetal alveolar type II cells. The data indicate that C/EBPs facilitate SP-A gene expression, possibly by overcoming transcriptional silencing.

Killing of Klebsiella pneumoniae by human alveolar macrophages

We investigated putative mechanisms by which human surfactant protein A (SP-A) effects killing of Klebsiella pneumoniae by human alveolar macrophages (AMs) isolated from bronchoalveolar lavagates of patients with transplanted lungs. Coincubation of AMs with human SP-A (25 microg/ml) and Klebsiella resulted in a 68% decrease in total colony forming units by 120 min compared with AMs infected with Klebsiella in the absence of SP-A, and this SP-A-mediated effect was abolished by preincubation with N(G)-monomethyl-L-arginine. Incubation of transplant AMs with SP-A increased intracellular Ca(2+) concentration ([Ca(2+)](i)) by 70% and nitrite and nitrate (NO(x)) production by 45% (from 0.24 +/- 0.02 to 1.3 +/- 0.21 nmol small middle dot 10(6) AMs(-1).h(-1)). Preincubation with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester inhibited the increase in [Ca(2+)](i) and abrogated the SP-A-mediated Klebsiella phagocytosis and killing. In contrast, incubation of AMs from normal volunteers with SP-A decreased both [Ca(2+)](i) and NO(x) production and did not result in killing of Klebsiella. Significant killing of Klebsiella was also seen in a cell-free system by sustained production of peroxynitrite (>1 microM/min) at pH 5 but not at pH 7.4. These findings indicate that SP-A mediates pathogen killing by AMs from transplant lungs by stimulating phagocytosis and production of reactive oxygen-nitrogen intermediates.

GATA6 regulates differentiation of distal lung epithelium

GATA6 is a member of the GATA family of zinc-finger transcriptional regulators and is the only known GATA factor expressed in the distal epithelium of the lung during development. To define the role that GATA6 plays during lung epithelial cell development, we expressed a GATA6-Engrailed dominant-negative fusion protein in the distal lung epithelium of transgenic mice. Transgenic embryos lacked detectable alveolar epithelial type 1 cells in the distal airway epithelium. These embryos also exhibited increased Foxp2 gene expression, suggesting a disruption in late alveolar epithelial differentiation. Alveolar epithelial type 2 cells, which are progenitors of alveolar epithelial type 1 cells, were correctly specified as shown by normal thyroid transcription factor 1 and surfactant protein A gene expression. However, attenuated endogenous surfactant protein C expression indicated that alveolar epithelial type 2 cell differentiation was perturbed in transgenic embryos. The number of proximal airway tubules is also reduced in these embryos, suggesting a role for GATA6 in regulating distal-proximal airway development. Finally, a functional role for GATA factor function in alveolar epithelial type 1 cell gene regulation is supported by the ability of GATA6 to trans-activate the mouse aquaporin-5 promoter. Together, these data implicate GATA6 as an important regulator of distal epithelial cell differentiation and proximal airway development in the mouse.

Value of thyroid transcription factor-1 and surfactant apoprotein A in the differential diagnosis of pulmonary carcinomas: a study of 109 cases

Thyroid transcription factor-1 (TTF-1) and surfactant apoprotein A (SP-A) belong to tissue-specific markers expressed in the normal respiratory epithelium. Both proteins are expressed in some lung carcinomas, and they have potential diagnostic use. We performed an immunohistochemical study on 109 tumors to determine the usefulness of monoclonal SP-A (PE-10) and TTF-1 (8G7G3/1) antibodies in distinguishing primary and metastatic lung carcinomas ( n=54) from a broad spectrum of nonpulmonary tumors ( n=55). An immunoperoxidase method using a streptavidin-biotin kit was applied on paraffin sections. We found positive results for TTF-1 and SP-A in 75% and 46% of pulmonary adenocarcinomas and in 50% and 25% of pulmonary non-neuroendocrine large cell carcinomas (LCCs), respectively. Small cell lung carcinomas were TTF-1 positive in 89% of cases and completely negative for SP-A. Squamous cell carcinomas and carcinoid tumors were negative for both proteins. In the group of nonpulmonary tumors, TTF-1 was detected in 8 of 11 thyroid carcinomas and SP-A in 1 of 6 colorectal carcinomas. Other tumors, including seven cases of pleural mesothelioma, were negative for both TTF-1 and SP-A. The expression of both antibodies was independent of primary and metastatic sites of the tumor. We observed a significant decrease of SP-A immunoreactivity in poorly differentiated lung adenocarcinomas. The combination of anti-TTF-1 with anti-SP-A does not increase the diagnostic usefulness of TTF-1 alone. Because of its diagnostic utility TTF-1 should be added to a panel of antibodies used for assessing tumors of unknown origin.

Regulation of surfactant proteins by LPS and proinflammatory cytokines in fetal and newborn lung

Intra-amniotic lipopolysaccharide (LPS) and cytokines may decrease respiratory distress syndrome (RDS) and increase chronic lung disease in the newborn. The aim was to identify the primary inflammatory mediators regulating the expression of surfactant proteins (SP) in explants from immature (22-day-old fetus) and mature (30-day term fetus and 2-day-old newborn) rabbits. In immature lung, interleukin (IL)-1alpha and IL-1beta upregulated the expression of SP-A and SP-B. These effects of IL-1 were diminished, and SP-C mRNA was suppressed additively in the presence of tumor necrosis factor (TNF)-alpha and either LPS or interferon (IFN)-gamma. LPS, TNF-alpha, or IFN-gamma had no effect alone. In explants from the term fetus and the newborn, LPS, IL-1alpha, and TNF-alpha additively suppressed the SPs. LPS acutely induced IL-1alpha in alveolar macrophages in mature lung but not in the immature lung. IFN-gamma that generally has low expression in intrauterine infection decreased the age dependence of the other agonists' effects on SPs. The present study serves to explain the variation of the pulmonary outcome after an inflammatory insult. We propose that IL-1 from extrapulmonary sources induces the SPs in premature lung and is responsible for the decreased risk of RDS in intra-amniotic infection.

Transcriptional stimulation of the surfactant protein B gene by STAT3 in respiratory epithelial cells

The function of the lung is dependent upon differentiation and proliferation of respiratory epithelial cells and the synthesis/secretion of surfactant lipids and proteins into air space. During the respiratory inflammatory response, cytokines produced by macrophages and epithelial cells in the respiratory system have significant influence on surfactant protein homeostasis. We report here that among family members of Janus family tyrosine kinase (JAK) and signal transducers and activators of transcription (STAT), only JAK 1 and STAT3 stimulated the -500 to +41 promoter activity of the surfactant protein B (SP-B) gene in respiratory epithelial cells. JAK1 and STAT3 were co-localized in alveolar type II epithelial cells where SP-B is synthesized and secreted. Interleukin 6 and interleukin 11, known to activate STAT3 synergistically, stimulated the SP-B promoter activity with retinoic acid, which is at least partially mediated through interactions between STAT3 and retinoid nuclear receptor enhanceosome proteins in pulmonary epithelial cells.

Effects of simultaneous exposure of surfactant to serum proteins and free radicals

Free radicals (FRs) and serum proteins have both been implicated in the pathophysiology of surfactant dysfunction during acute lung injury (ALI). This study examines how these 2 distinct mechanisms interact to contribute to altered surfactant function in this setting. Calf lung surfactant (2 mg/mL) was incubated with no additives (C = control), and with low = (LD = 125 microM FeCl2; 250 microM H2O2) and high-dose (HD = 250 microM FeCl2, 500 microM H2O2) Fenton reaction reagents to generate hydroxyl radical. Each condition was studied with (1) no protein (N); and with 25%, 200%, and 800% (weight protein/weight phospholipid) protein added as (2) bovine albumin, (3) bovine fibrinogen, (4) hemoglobin, or (5) calf serum. Lipid (LFR) and protein (PFR) free-radical products, and modifications in the tertiary structure of Surfactant Protein A (SPA) on Western blot, were observed in N LD and N HD samples. Added proteins reduced LFR and PFR changes as well as SPA structural changes. Protection was greatest for fibrinogen, hemoglobin, and serum, and least for albumin. Minimal to no dysfunction, assayed by pulsating surfactometry, was observed in all samples. These findings indicate that addition of serum proteins to surfactant at 2 mg/mL protects against, rather than promotes, FR-mediated chemical changes in surfactant lipid and protein constituents.

Absence of SP-A modulates innate and adaptive defense responses to pulmonary influenza infection

Mice lacking surfactant protein SP-A [SP-A(-/-)] and wild type SP-A(+/+) mice were infected with influenza A virus (IAV) by intranasal instillation. Decreased clearance of IAV was observed in SP-A(-/-) mice and was associated with increased pulmonary inflammation. Treatment of SP-A(-/-) mice with exogenous SP-A enhanced viral clearance and decreased lung inflammation. Uptake of IAV by alveolar macrophages was similar in SP-A(-/-) and SP-A(+/+) mice. Myeloperoxidase activity was reduced in isolated bronchoalveolar lavage neutrophils from SP-A(-/-) mice. B lymphocytes and activated T lymphocytes were increased in the lung and spleen, whereas T helper (Th) 1 responses were increased [interferon-gamma, interleukin (IL)-2, and IgG(2a)] and Th2 responses were decreased (IL-4, and IL-10, and IgG(1)) in the lungs of SP-A(-/-) mice 7 days after IAV infection. In the absence of SP-A, impaired viral clearance was associated with increased lung inflammation, decreased neutrophil myeloperoxidase activity, and increased Th1 responses. Because the airway is the usual portal of entry for IAV and other respiratory pathogens, SP-A is likely to play a role in innate defense and adaptive immune responses to IAV.

Alterations in lung collectins in an adaptive allergic immune response

Although surfactant apoproteins are known to be mediators of innate responses, their relationship to adaptive responses has not been examined extensively. We investigated possible links between surfactant apoproteins and responses to allergens by studying alterations in surfactant apoproteins A, B, and D in a murine model of allergic pulmonary inflammation. Three murine strains (BALB/c, C57BL/6, and 129J) demonstrated increased immunostaining of surfactant apoproteins A and D in nonciliated epithelial cells of noncartilaginous airways after aerosolized challenge. In contrast, surfactant apoprotein B immunostaining was unchanged. Immunoblotting demonstrated increased surfactant A in bronchoalveolar lavage fluid after allergen sensitization and challenge. Surfactant apoprotein A and D induction required T and/or B lymphocyte responses to allergen, since the induction was absent in recombinase-activating gene-deficient mice, which lack functional lymphocytes. We conclude that increased immunoreactivity of two collectins, surfactant apoproteins A and D, occurs within the response to allergen. Our findings support a model in which surfactant apoproteins A and D are important to both innate immunity and adaptive immune responses to allergens.

Antisense inhibition of surfactant protein A decreases tubular myelin formation in human fetal lung in vitro

Surfactant protein A (SP-A) is the most abundant of the surfactant-associated proteins. SP-A is involved in the formation of tubular myelin, the modulation of the surface tension-reducing properties of surfactant phospholipids, the metabolism of surfactant phospholipids, and local pulmonary host defense. We hypothesized that elimination of SP-A would alter the regulation of SP-B gene expression and the formation of tubular myelin. Midtrimester human fetal lung explants were cultured for 3-5 days in the presence or absence of an antisense 18-mer phosphorothioate oligonucleotide (ON) complementary to SP-A mRNA. After 3 days in culture, SP-A mRNA was undetectable in antisense ON-treated explants. After 5 days in culture, levels of SP-A protein were also decreased by antisense treatment. SP-B mRNA levels were not affected by the antisense SP-A ON treatment. However, there was decreased tubular myelin formation in the antisense SP-A ON-treated tissue. We conclude that selective elimination of SP-A mRNA and protein results in a decrease in tubular myelin formation in human fetal lung without affecting SP-B mRNA. We speculate that SP-A is critical to the formation of tubular myelin during human lung development and that the regulation of SP-B gene expression is independent of SP-A gene expression.

Surfactant protein A inhibits peptidoglycan-induced tumor necrosis factor-alpha secretion in U937 cells and alveolar macrophages by direct interaction with toll-like receptor 2

Pulmonary surfactant protein A (SP-A) plays an important role in modulation of the innate immune system of the lung. Peptidoglycan (PGN), a cell wall component of Gram-positive bacteria, is known to elicit excessive proinflammatory cytokine production from immune cells. In this study we investigated whether SP-A interacts with PGN and alters PGN-elicited cellular responses. Binding studies demonstrate that PGN is not a ligand for SP-A. However, SP-A significantly reduced PGN-elicited tumor necrosis factor alpha (TNF-alpha) secretion by U937 cells and rat alveolar macrophages. The inhibitory effect on TNF-alpha secretion was dependent upon SP-A concentrations in physiological range. Coincubation of SP-A and PGN with human embryonic kidney 293 cells that had been transiently transfected with the cDNA of Toll-like receptor 2 (TLR2), a cell signaling receptor for PGN, significantly attenuated PGN-induced nuclear factor-kappaB activity. SP-A directly bound to a soluble form of the recombinant extracellular TLR2 domain (sTLR2). Coincubation of sTLR2 with SP-A significantly reduced the binding of sTLR2 to PGN. These results indicate that the direct interaction of SP-A with TLR2 alters PGN-induced cell signaling. We propose that SP-A modulates inflammatory responses against the bacterial components by interactions with pattern-recognition receptors.

Increased circulating levels of soluble Fas ligand are correlated with disease activity in patients with fibrosing lung diseases

OBJECTIVE

The Fas-Fas ligand (FasL) pathway is one of the important apoptosis-signalling molecule systems. We previously determined that this pathway may be involved in the pathogenesis of fibrosing lung diseases. In the present study, we evaluated the clinical significance of the levels of soluble forms of Fas (sFas) and FasL (sFasL) in serum from patients with fibrosing lung diseases.

METHODOLOGY

We measured sFas, sFasL, KL-6 (a measure of alveolar type II cell damage), surfactant protein D (SP-D), and surfactant protein A (SP-A) levels in serum from 35 patients with idiopathic pulmonary fibrosis (IPF), 17 patients with interstitial pneumonia associated with collagen vascular diseases (CVD-IP), and 13 normal healthy controls using enzyme-linked immunosorbent assays (ELISA).

RESULTS

The serum levels of sFasL were significantly increased in patients with active IPF and CVD-IP, compared with those with inactive disease and controls. There was no significant difference in sFasL levels between patients with inactive disease and controls. Serum sFasL levels were significantly correlated with lactate dehydrogenase and KL-6 levels in IPF. The decrease in sFasL levels following corticosteroid therapy was not correlated with the clinical course of IPF. There was no significant difference in serum sFas levels between IPF or CVD-IP patients and controls.

CONCLUSIONS

Although further studies need to be performed on a large number of patients with histologically proven IPF or CVD-IP, it would seem that serum sFasL levels may reflect the activity of IPF and CVD-IP.

Surfactant protein-A--deficient mice display an exaggerated early inflammatory response to a beta-resistant strain of influenza A virus

Surfactant protein (SP)-A is a member of the collectin family of proteins. In vitro, SP-A binds influenza A virus (IAV), neutralizes infectivity, and enhances uptake by macrophages. SP-D also binds and neutralizes certain strains of IAV. To determine if SP-A has a role in protecting the intact animal against IAV infection, we inoculated gene-targeted SP-A-deficient mice (-/-) and littermate controls (+/+) with either saline or increasing doses of an IAV strain that binds SP-A but not SP-D. IAV was more virulent in SP-A-/- compared with +/+ mice, with a significantly lower mean lethal dose (LD(50)) and significantly greater weight loss during infection. SP-A-/- mice also had increased airway epithelial injury and more alveolar cellular infiltrates than +/+ mice. On Day 2, SP-A-/- mice had more neutrophils and higher MIP-2 levels in the lung than +/+ mice. We conclude the altered host response and increased susceptibility to X-79Delta167 infection in SP-A-/- mice reflects a protective role for SP-A in regulating the host response to IAV. Because the recovery of virus from lung homogenates on Days 2 and 6 after inoculation was comparable in -/- and +/+ mice, we speculate SP-A reduces IAV virulence independently of direct viral neutralization.

An ELISA technique for quantification of surfactant apoprotein (SP)-C in bronchoalveolar lavage fluid

Pulmonary surfactant apoprotein C (SP-C) is a small, unique peptide that contributes to the reduction of alveolar surface tension. Due to the extreme hydrophobic nature of this peptide it was hitherto not possible to quantify SP-C in biological samples by immunological techniques. Using a newly developed polyclonal antibody raised against recombinant human SP-C in rabbits, we now describe an enzyme-linked immunosorbent assay (ELISA) to quantitate SP-C in bronchoalveolar lavage fluid (BALF). Solid phase binding of the hydrophobic SP-C was achieved by transfer of the standard or BALF samples (diluted in 80% isopropanol, pH 3.5) to polystyrene microtiter plates. Sequential treatment with trifluoroethanol and methanol (2x) was employed to improve antigen presentation and to minimize the influence of phospholipids. With this assay, SP-C from human, rabbit, porcine, and bovine surfactant was detectable. No cross-reactivity of the antibody to human SP-A and monomeric and dimeric SP-B was encountered. Total serum proteins did not affect ELISA signals, as evident from spiking experiments. The detection limit of the ELISA ranged below 3 ng/ml, and intra- and interassay coefficients of variation were 3.5% (n = 16) and 5.3% (n = 6), respectively. Serial dilutions of BALF showed good linearity, and excellent recovery rates were obtained upon spiking of human BALF. A mean value of 579.5 +/- 45.9 ng/ml (mean +/- SEM) SP-C was found in BALF samples of human healthy volunteers (n = 22), corresponding to 26.61 +/- 1.91 microg SP-C/mg total phospholipids (PL). SP-C levels were significantly lower in BALF of patients with acute respiratory distress syndrome (ARDS) (286.9 +/- 19.8 ng/ml [p < 0.001]; 13.92 +/- 1.93 microg SP-C/mg PL [p < 0.001], n = 48). We conclude that SP-C may be quantified with high specificity, reproducibility, and sensitivity in bronchoalveolar lavage samples by the presently described ELISA technique and that SP-C levels are significantly decreased in ARDS.

SP-A-enriched surfactant for treatment of rat lung transplants with SP-A deficiency after storage and reperfusion

BACKGROUND

The function of pulmonary surfactant is affected by lung transplantation, contributing to impaired lung transplant function. A decreased amount of surfactant protein-A (SP-A) after reperfusion is believed to contribute to the impaired surfactant function. Surfactant treatment has been shown to improve lung transplant function, but the effect is variable. We investigated whether SP-A enrichment of surfactant improved the efficacy of surfactant treatment in lung transplantation.

METHODS

Left and right lungs of Lewis rats, inflated with 50% O2, were stored for 20 hr at 8 degrees C. Surfactant in bronchoalveolar lavage fluid from right lungs was investigated after storage (n=6). Left lungs were transplanted into syngeneic recipients and treated with SP-A-deficient surfactant (n=6) or SP-A-enriched surfactant (n=6) just before reperfusion. Air was instilled into untreated lung transplants (n=6). Sham operated (n=4) and normal (n=8) animals served as controls. Lung function was measured during 1 hr of reperfusion; surfactant components in bronchoalveolar lavage fluid were measured after reperfusion.

RESULTS

After storage the amount of SP-A decreased by 27%, whereas surfactant phospholipids changed minimally. After reperfusion a further decrease of SP-A was paralleled by profound changes in surfactant phospholipids. Lung transplant function, however, remained relatively good. After instillation of SP-A-enriched surfactant, PO2 values were reached that approximated sham control PO2 values, whereas after SP-A-deficient surfactant treatment, the PO2 values did not improve.

CONCLUSION

Enrichment of surfactant with SP-A for treatment of lung transplants improves the efficacy of surfactant treatment.

Increased expression of thyroid transcription factor-1 (TTF-1) in respiratory epithelial cells inhibits alveolarization and causes pulmonary inflammation

Thyroid transcription factor-1 (TTF-1), a member of the Nkx2 family of homeodomain-containing transcription factors, is expressed in the epithelium of the lung. TTF-1 is a critical regulator of transcription for the surfactant proteins (SP) A, B, and C and is essential for lung morphogenesis. Sites and levels of TTF-1 expression vary during lung morphogenesis and following injury. In order to determine the role of TTF-1 in lung formation, transgenic mice were generated in which TTF-1 was expressed in respiratory epithelial cells of wild-type and Ttf1 null mutant (-/-) mice, using the lung-specific SP-C promoter. The SP-C-Ttf1 transgene did not rescue the severe pulmonary hypoplasia characteristic of the Ttf1 (-/-) mice. Increased expression of TTF-1, however, caused dose-dependent alterations in postnatal lung morphology of wild-type mice. Modest overexpression of TTF-1 caused type II cell hyperplasia and increased the cellular content of SP-B. In contrast, higher expression levels of TTF-1 disrupted alveolar septation, causing emphysema. In mice with the highest transgene expression, TTF-1 caused severe inflammation, pulmonary fibrosis, respiratory failure, and death, associated with eosinophil infiltration and increased expression of eotaxin and IL-6. Increased expression of TTF-1 altered alveolarization and caused chronic pulmonary inflammation, demonstrating that precise regulation of TTF-1 is critical for homeostasis in the postnatal lung.

Pulmonary surfactant and inflammation in septic adult mice: role of surfactant protein A

Surfactant alterations, alveolar cytokine changes, and the role of surfactant protein (SP)-A in septic mice were investigated. Sepsis was induced via cecal ligation and perforation (CLP). Septic and sham mice were euthanized at 0, 3, 6, 9, 12, 15, and 18 h after surgery. Mice deficient in SP-A and mice that overexpressed SP-A were euthanized 18 h after surgery. In wild-type, sham-operated mice, surfactant pool sizes were similar at all time points, whereas in the CLP groups there was a significant decrease in small-aggregate surfactant pool sizes beginning 6 h after CLP. Interleukin-6 concentrations in bronchoalveolar lavage fluid from septic animals increased from 6 to 18 h after surgery. Identical surfactant alterations and concentrations of cytokines were observed in septic mice that were SP-A deficient or that overexpressed SP-A. In conclusion, alterations of pulmonary surfactant and alveolar cytokines occur simultaneously, 6 h after a systemic insult. In addition, we did not detect a role for SP-A in regulating surfactant phospholipid pool sizes or pulmonary inflammation in septic mice.

Maintenance of surfactant protein A and D secretion by rat alveolar type II cells in vitro

Secretion of surfactant proteins A and D (SP-A and SP-D) has been difficult to study in vitro because a culture system for maintaining surfactant secretion has been difficult to establish. We evaluated several growth factors, corticosteroids, rat serum, and a fibroblast feeder layer for the ability to produce and maintain a polarized epithelium of type II cells that secretes SP-A and SP-D into the apical medium. Type II cells were plated on a filter insert coated with an extracellular matrix and were cultured at an air-liquid interface. Keratinocyte growth factor (KGF) stimulated type II cell proliferation and secretion of SP-A and SP-D more than fibroblast growth factor-10 (FGF-10), hepatocyte growth factor (HGF), or heparin-binding epidermal-like growth factor (HB-EGF). Cells cultured in the presence of KGF and rat serum with or without fibroblasts had high surfactant protein mRNA levels and exhibited a high level of SP-A and SP-D secretion. Dexamethasone inhibited type II cell proliferation but increased expression of SP-B. In the presence of KGF, rat serum, and dexamethasone, the mRNAs for the surfactant proteins were maintained at high levels. Secretion of SP-A and SP-D was found to be independent of phospholipid secretion.

Association between surfactant protein A gene locus and severe respiratory syncytial virus infection in infants

Respiratory syncytial virus (RSV) causes seasonal epidemics of bronchiolitis among susceptible infants. Surfactant protein A (SP-A), a lung C-type lectin involved in innate host defense, opsonizes RSV and enhances phagocytosis. The candidate gene approach was used to investigate association of SP-A polymorphism with susceptibility to severe RSV infection. Genotype analysis was done for 86 infants with severe RSV infection and 95 matched control subjects. A significant difference in the frequency of SP-A2 was observed. The SP-A2 allele 1A(3) was overrepresented in RSV-infected infants, compared with control subjects (5% vs. 0.5%; P =.006), whereas allele 1A was underrepresented (1% vs. 6%; P =.011). The allele pool in which lysine was amino acid 223 was overrepresented in infants with severe RSV infection (28% vs. 18%; P =.023), whereas the allele pool in which proline was amino acid 99 was underrepresented (5% vs. 16%; P =.001). These results indicate that a genetic association exists between SP-A gene locus and severe RSV infection.

Two-dimensional cell sheet manipulation of heterotypically co-cultured lung cells utilizing temperature-responsive culture dishes results in long-term maintenance of differentiated epithelial cell functions

Here we report two-dimensional cell sheet manipulation (2D CSM) of heterotypically co-cultured lung cell sheets and the maintenance of differentiated phenotypes of lung epithelial cells over prolonged periods of up to 70 days. This was facilitated by poly(N-isopropylacrylamide) (PIPAAm)-grafted tissue culture dishes. PIPAAm-grafted dishes are responsive to temperature changes and offer a unique surface on which cells adhere and multiply like on ordinary tissue culture dishes under the permissive temperature of 37 degrees C, but on lowering of temperature resulting in changes in hydration of the polymer the cells spontaneously detach from the surface without use of enzymes like trypsin which is the common procedure. It has been well documented that type II pneumocytes of the lung lose many of their special features rapidly in culture. The culture system detailed here comprises random co-culture of epithelial and mesenchymal cells of lung. The heterotypic cell culture system promotes cell-cell interactions maintaining a harmonized physiology. When this heterotypic monolayer on PIPAAm-grafted dishes was subjected to lower temperature of 20 degrees C and 2D CSM we were able to transfer the monolayer as a single contiguous sheet with cell-cell connections intact to other surfaces. This non-invasive transfer of cell sheet resulted in shrinkage of the monolayer, enabling the type II cells to regain their cuboidal morphology and specialized characters like Maclura pomifera lectin binding and surfactant protein A (SP-A) expression. The active dome formation also observed subsequent to transfer reaffirms the uniqueness of the culture conditions and 2D CSM in future for developing tissue like architecture in vitro.